Anyone who has ever followed British tabloids’ coverage of Germany (“Germans declare war on our pound”) will know that some of the divisions of World War II have yet to fully disappear.

That’s even more true for two countries that 70 years later are actually still at war: Japan and Russia.

It turns out that the two countries never signed a peace treaty after World War II — and the world would probably have forgotten about that unresolved chapter of world history were they not seeking peace now. Russian President Vladimir Putin and his Japanese counterpart Shinzo Abe brought the issue back into the spotlight Wednesday when they suggested that they would seek common ground for an official peace deal more than 70 years after the end of hostilities.

Such mutual enthusiasm isn’t always expressed by countries facing similar issues. South Korea and North Korea are still technically at war — and while both countries have indicated they're willing to sign a treaty, it turns out that making peace isn’t always that easy. Given that they were parties to a 1953 armistice that stopped hostilities, Beijing and Washington would likely have to give their approval to all conditions of a full peace deal, as well. There are some historic examples, too, including the Principality of Montenegro that was legally at war with Japan between 1904 and 2006. At the time, Montenegro supported Russia in its brief clash with Japan. But the principality wasn’t a party to the 1905 peace treaty. After it became part of Yugoslavia, it was unable to settle the conflict on its own because it no longer existed as a country. Its legal state of war with Japan only ended when it gained independence in 2006, more than 100 years after hostilities began.

So, what has so far stopped Russia and Japan from overcoming their divisions? As it is often the case with Moscow, there’s some disputed land involved. Japan and Russia have both made claims on a chain of four islands in the Pacific Ocean located between Russia’s Kamchatka Peninsula and Japan’s most northern main island, Hokkaido.

During the war, the Soviet Union and Japan were not involved in direct fighting until the very end. On Aug. 9, 1945, the Soviet Union decided to invade Manchukuo, a Japanese puppet state in what today constitutes northeastern China. The invasion came three days after the United States had dropped an atomic bomb over Japan’s Hiroshima. While Japan was already about to concede defeat amid pressure from all sides, the Soviet Union’s surprising attack forced the Japanese to surrender without conditions. (The Japanese were hoping for the Soviets to act as a neutral negotiator before the Aug. 9 attack.)

After Japan’s defeat, the Soviet Union claimed the four islands in Japan’s north, arguing that Japan stole them from Russia in the first place when it annexed them in the 19th century. But the Japanese refused to acknowledge Russia’s claims and only signed a declaration that ended the state of war in 1956, while still refusing to sign an actual peace treaty.

It’s unclear how Russia and Japan are planning to find a solution to this muddled situation.

Russia has previously offered to give up two of the four islands. But after Putin rallied his supporters, saying that the annexation of Crimea was a sign of love for the Russian motherland, any more substantial territorial concessions in the Pacific Ocean would be difficult for him to explain. As in Crimea, there are also some strategic considerations behind Russia's claims in the Pacific, as the four islands are located in waters frequented by Russian submarines.

Meanwhile, Japan has insisted that it seeks total control of all four islands and a spokesman for the Japanese government said Wednesday that the country's position had not changed. Giving in to Russian demands would also pose some domestic challenges to Japanese leader Abe, who has sought to redraw Japan’s pacifist constitution.

In 2015, Abe was widely criticized for not repeating a 1995 statement, in which the Japanese government offered a “heartfelt apology” for Japan’s “colonial rule and aggression.” At the time, the careful wording was interpreted as a balancing act to win over nationalist supporters while preventing fury in China or the United States. Any conditions of a peace treaty between Russia and Japan would face the same scrutiny.

Ironically, the relationship between Japan and its archenemy China proves that peace treaties can be signed despite lingering territorial disputes. Japan and China both claim two sets of small, uninhabited islands in the East China Sea, called Senkaku by the Japanese and Diaoyu by the Chinese. The two countries still managed to sign a peace treaty in 1978.